She called to say she'd be "hanging out" at a friend's house, but you continue to worry. With each passing car, you stare out the window, hoping that's her. You haven't had a good night's sleep in two months.

At last ... she's home. You're too relieved to scold her. You want her last weeks with you to be quality time before she heads off to college.

Besides, she'll accuse you of not trusting her. She'll also tell you she hates you! Better to go to bed and prepare for tomorrow.

Welcome to the summer after high school graduation, when the nicest kids turn into monsters and the coolest, calmest parents turn into nervous wrecks. For what was the Class of 2004, it's freedom and exhilaration. For their parents it's a descent into hell.

But don't assume your child is the only "monster" out there -- they're all monsters! And they're all normal, decent human beings. They're going through a separation process that began at birth, accelerated during the "Terrible Twos" and continues this summer. It's a necessary and important stage in their development as independent, responsible adults.

According to psychologist Laurence Steinberg: "Many parents erroneously equate their teenager's drive for independence with rebelliousness, disobedience or disrespect. It's healthy for adolescents to push for autonomy. They need to learn to be self-reliant."

In the United States, parents admire self- reliance and would like to see their children achieve a strong sense of independence before college. Who wants to deal with daily, distraught phone calls and desperate e-mails from a homesick kid?

In Japan, however (and among many Asian families in Hawaii), youngsters are less enthusiastic about independence.

Family harmony is stressed, but this often delays the transition to adulthood.

But gaining independence is much more than learning survival skills. To make a successful transition from childhood to adulthood, children must separate psychologically from their parents, establish their own identities and adopt their own values -- values that often oppose "authority" (i.e., parents). No matter what parents consider appropriate, children must decide for themselves: Should I drink? How much? Have sex? Try drugs?

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Sure, they're having fun, but don't they know their anxious parents are home waiting for a call from the police?

According to Karen Coburn and Madge Treeger, authors of "Letting Go: A Parents' Guide to Understanding the College Years," the answers to these questions have been forming since early childhood, but "college life brings them face-to-face with more choices than they have ever had before ... with no familiar parental boundaries to keep them in line."

Children might not like their parents' rules, but "they depend on these rules to keep their behavior within safe limits. Sometimes college students don't realize that this parental backing is missing until they are in the midst of a problematic situation. No one in college will be checking to see when they come home, or even if they come home. ... Students have to put themselves on the line; they are responsible for setting their own limits."

There are other reasons that this summer will be difficult -- biological reasons. According to a May 10 Time magazine article, the adolescent brain is very much a work in progress; indeed, the brain doesn't reach full maturity until age 25. What kind of behavior can we expect?

Psychiatrist Ronald Dahl notes that with adolescents, "There is some particular hormone-brain relationship contributing to the appetite for thrills, strong sensations and excitement." The Time article goes on to observe: "This thrill-seeking may have evolved to promote exploration, an eagerness to leave the nest and seek one's own path and partner. But in a world where fast cars, illicit drugs, gangs and dangerous liaisons beckon, it also puts the teenager at risk."

The tragic death of 18-year-old Saint Louis graduate John Siofele a few years back reminds us of this risk. At 4:06 a.m., Siofele's car crossed the center line on Farrington Highway and plowed into a bus.

Child psychologist Richard Baron tells us another reason for this difficult summer: "Children intentionally try to distance themselves from their parents by setting up 'angry' situations that lead to battles and endlessly arguing over anything -- in order to make the end-of-summer separation less difficult."

Graduation summer, then, is a time of experimenting, breaking away, establishing one's own values and preparing for separation, resulting in a painfully necessary war between parent and child. Advice for parents: Don't allow your child to become too "wild," and don't allow yourselves to become too "severe."

Conflicts will not be confined to any particular group, nor income level. Kids headed for Harvard are just as likely to rebel as kids headed for the University of Hawaii. What to expect? It's not a pretty picture.

With egos inflated by commencement praise, zero homework, nightly parties and pockets full of cash, the graduate's behavior undergoes a drastic change -- often for the worse. Mild-mannered Jennifer, who in April was a model student and a perfect daughter, now smokes pot and calls her mother a "bitch."

Battles will be waged after dark -- way after dark. No matter how lenient, parents' rules will come under attack. You'd like to see your 18-year-old daughter home by midnight, but this is "too confining." Midnight is when she's just warming up. You and your mate are groggy. She's wide awake. You skirmish and negotiate by way of cell phones. You try to hold the line, but she's demanding sunrise.

Whatever parents disapprove of will be high on their child's "must do" list: drinking, smoking, sex, drugs and night-clubbing. By one report, by graduation, 10-15 percent of Hawaii high schools kids are already into drugs (primarily marijuana) and 30-35 percent drink on a regular basis. Vodka is often the drink of choice.

Drinking will take place after the clubbing -- in public places (parks, beaches) or at a friend's place. Amazingly, some parents will allow drinking at their homes despite the fact that 1) it's illegal for under-21-year-olds, and 2) they will be liable if a child leaves their dwelling inebriated and hurts himself or herself, or someone else.

Sneaking around and lying are commonplace; indeed, lying is one of the most frequently used weapons against parents. Kids will turn the folks off the drinking trail by saying they are going to a late-night movie or staying overnight at a friend's house.

Swearing reaches epidemic proportions, with the "F" word used constantly. Whatever happened to the child in braces and ponytail, all hugs and kisses?

College is often described as "the best time of your life," but for grads it's fear and loathing. Ever since junior high, they've detested the "c" word. This is especially true of Hawaii kids going off to the mainland, which many view as a foreign nation with all its dangers and uncertainties. So, as September approaches and anxiety levels increase, they cling nervously together, like a troop of commandos heading into combat. At no time in their lives will they feel so attached to their friends. Before each goes through security at the airport, there will be tears and hugs because they sense their relationship will never be the same.

After Hell Summer the dreaded "tearful farewell" might not be so dreaded or tearful. It's been bad, but the grads have grown a tremendous amount. Remarkably, summer events have made them much more capable of handling the stresses and challenges that lie ahead.

What can you do to make the summer more productive and less agonizing?

>> Form an inseparable team with your spouse and agree on the major issues, like curfew. Handling a teenager takes (at least!) two people.

>> Talk. If you're the parents of a graduating senior, it might be too late to tell you this, but other parents, take note. Start now! Bond with your children to the point where they will tell you if they drink or have sex. And don't hit them over the head if they do. In college, risky behavior might increase 100-fold, and you're not going to know anything about it. If they don't confide in you in high school, they won't confide in you in college, where the situation could be far more dangerous and traumatic.

Authors Coburn and Treeger quote a sophomore in college who spent her first few months in turmoil after experimenting with drugs and alcohol:

"The only thing I wish is that my parents had prepared me better. ... There was never a real discussion about sex, drugs or even money management. They just trusted me to do my best ... but it's college. College is a chance to taste every temptation you could imagine. I'm not sure how you can prepare a person for this other than talking about it. Just talk."

>> Get to know other parents. Hold a party and invite both your child's friends and their folks. You can share experiences with other parents and form a support group. If possible, arrange some activities where both kids and parents can discuss what lies ahead in college.

>> Be realistic about setting rules. Steinberg writes that next to love, parents need to give structure to their children's lives. "Even teenagers need rules and limits. Be firm, but fair. Relax your rules bit by bit as your child demonstrates more maturity."

Lighten up on the curfew, but don't allow all-nighters because it's not wise to be out in Hono-lulu (or Hilo, Kahului or Lihue) in the early morning, especially after the bars start closing at 2 o'clock. Don't cave in when they argue that they won't have a curfew in college. They're at home, and it's your home. No matter what hour you agree on, insist on their telling you their plans: what, where, when and with whom. It's for their own safety.

>> Start planning for college. The transition will be a lot easier if you start arranging some fun, pre-college activities, like shopping for clothes and a laptop or assembling remembrances of home. Correspond with the future roommate to get acquainted and plan things ("Are you bringing a rice cooker?").

>> Read "Letting Go." This book will be enormously helpful in understanding what your child will be going through.

In sum, it's important to understand that the separation process, which we, as parents, experienced with the "Terrible Twos," has come back with a vengeance the summer after high school graduation. It's a painful but necessary step along the road to adulthood.

C. Richard Fassler is the author of "Rainbow Kids." His latest book, "Hawaii's College Guide, from Pre-school to High School" will be published this fall.